The present invention relates to a fender designed to protect a vessel by reducing the impact of the docking vessel through absorption of the kinetic energy thereof.
A fender 9 conventionally used in the art is exemplified by a circle-type fender made of one piece rubber material having a sectional shape as shown in FIG. 20A. The circle-type fender 9 includes: a first bumper member 91 formed in a cylindrical shape of a constant outside diameter and constructed such that one end of the cylindrical body defines a distal end 9a of the fender 9 and serves as a fixing portion for fixing an impact receiving plate (not shown) directly coming into contact with a vessel; and a second bumper member 92 formed in a hollow conical shape wherein one end thereof is connected to the other end of the cylindrical body of the first bumper member 91 while the other end thereof defines a fix portion to be fixed to a fixing surface Q on a dock and wherein the latter end thereof has a greater outside diameter than the former end thereof. Indicated at 93 is a flange actually functioning to fix the fix portion of the second bumper member 92 to the fixing surface Q.
When receiving a compressive force from the docking vessel, the fender 9 is compressively deformed as described below. First, the fender 9 develops a reaction force against the compressive force. When the fender can no more withstand the compressive force, it starts to buckle at an outer periphery of a connection portion CP between the first bumper member 91 and the second bumper member 92 and at an inner periphery of a buckling position BP of the second bumper member 92. Subsequently, as shown in FIG. 20B, the whole body of the fender 9 is deformed into a tightly folded shape with an outer periphery 91a of the first bumper member 91 and an outer periphery 92a of the second bumper member 92 as well as areas 92b, 92c above and below the buckling position BP on the inner periphery of the second bumper member 92 coming into contact with each other. Then, the tightly folded fender 9 with no more portion to be buckled forms a single rubber mass which is further compressively deformed.
If this process is expressed by a distortion-reaction force characteristic curve plotting the amount of distortion of the compressed fender 9 relative to the reaction force developed in the fender 9, a solid curved line of FIG. 21 is obtained. Specifically, a line portion between the origin O and Maximum Point A corresponds to a period between a normal state shown in FIG. 20A and a state just before the fender starts to buckle, yielding to the compressive force. During this period, the compressed fender 9 develops the reaction force, trying to restore itself to its initial shape. The reaction force increases as the amount of distortion becomes greater. Upon buckling, however, the fender 9 loses most of the reaction force. Hence, the reaction force declines during the time that the fender 9 is crushed into the state of FIG. 20B. This time period corresponds to a line portion between Maximum Point A and Minimum Point C of the characteristic curve. In the state of FIG. 20B, the whole body of the fender 9 behaves as a single rubber mass as mentioned supra, developing the reaction force again. Therefore, the reaction force substantially linearly rises from Minimum Point C.
The practically useful range of the fender 9 with such a characteristic curve is limited to a range between the origin O and a point B representing the same level of reaction force as Maximum Point A. The useful range as expressed in terms of distortion is limited to the range of not more than D. This is because a distortion in excess of D means an excessive reaction force which, in turn, will cause damage to the vessel or to the fender 9 itself. The amount of energy that the fender 9 can absorb through distortion D within the allowed range is represented by an area S1 of a region enclosed by the characteristic curve represented by the solid line, a horizontal axis O-D, and a vertical line B-D.
It is generally thought idealistic that the fender is capable of absorbing such an amount of energy that corresponds to the combination of the above area S, and an area S2 of a region enclosed by the characteristic curve and a horizontal line A-B. However, the fender is actually capable of absorbing energy of an amount reduced by that represented by the area S2, thus reduced in the energy absorption efficiency.
In this connection, study has been made to increase the energy-absorption capacity of the fender 9. For instance, it is contemplated to increase thicknesses T1 and T2 of the first and second bumper members 91, 92, as shown in FIG. 22A, thereby to increase the reaction forces of the bumper members 91, 92 against compression.
Unfortunately, this approach has the following problem. With a smaller distortion than in the case of FIGS. 20A, 20B, the fender 9 is buckled into a completely folded state, as shown in FIG. 22B, wherein the outer periphery 91a of the first bumper member 91 and the outer periphery 92a of the second bumper member 92 as well as the areas 92b, 92c above and below the buckling position BP on the inner periphery of the second bumper member 92 come into contact with each other, leaving no more portion to be buckled. That is, with a smaller distortion than in the case of FIG. 20B, the buckled fender 9 starts to behave as the single rubber mass.
As indicated by a dash-single-dot curved line in FIG. 23, this results in a smaller distortion Dxe2x80x2 than the distortion D in the case of FIGS. 20A, 20B, the distortion Dxe2x80x2 corresponding to the reaction force which, after buckling, starts to re-increase and reaches a point Bxe2x80x2 representing the same level as Maximum Point Axe2x80x2. That is, a width of a constant load area in which the fender is principally involved in the energy absorption, or the range A-B between Maximum Point A and the point B of the characteristic curve is reduced to a range Axe2x80x2-Bxe2x80x2. Thus, the fender is reduced in the energy-absorption capacity after buckling.
Therefor, the arrangement of FIG. 22A suffers a problem that despite the increased size corresponding to the increased thickness as described above, the fender cannot attain the increased energy-absorption capacity corresponding to the size increase or any increase in the energy-absorption capacity at all.
A first object of the invention is to provide a novel fender capable of approximating a distortion-reaction force characteristic curve within an allowed range of distortion to an idealistic curve representing a substantially constant value of reaction force after the maximum point.
A second object of the invention is to provide a novel fender capable of presenting the greatest possible energy-absorption capacity within the allowed range of distortion.
According to the invention of claim 1, a fender for absorbing the impact of a vessel, formed of rubber and fixed to a fixing surface of a dock as having an impact receiving plate secured to a distal end of its body, the fender comprising: a first bumper member formed in a cylindrical shape of a constant outside diameter and defining at one end of the cylindrical body thereof a fixing portion for the impact receiving plate; a second bumper member connected at one end to the other end of the cylindrical body of the first bumper member, defining at the other end thereof a fix portion to be fixed to the fixing surface, formed in a hollow conical shape with its latter end greater in outside diameter than its former end, and buckling radially outwardly upon receiving a compressive force from the vessel thereby absorbing the impact of the vessel; and a step formed along an outer periphery of a connection portion between the two bumper members, the step defined by the former end of the second bumper member having a greater outside diameter than the latter end of the first bumper member.
By virtue of a step 14 on the outer periphery of the connection portion between two bumper members 11, 12, such as shown in FIGS. 1 and 2A for example, the fender of claim 1 can accomplish the increase in the aforesaid distortion D, as compared with the conventional fender 9 without the step on the outer periphery of the connection portion CP. Specifically, the provision of the step 14 provides a configuration wherein an outer periphery 11a of the first bumper member 11 is somewhat recessed from an outer periphery 12a of the second bumper member 12. As a result, when the fender is buckled, a greater distortion D than in the conventional fender 9 is involved in bringing the outer peripheries 12a, 12a into contact with each other, as shown in FIG. 2B.
As shown in FIG. 20B, the conventional fender 9 in the buckled state contains a cavity CV between the bent bumper members 91, 92. The cavity CV is responsible for a greater decline of the reaction force after Maximum Point A. That is, a deformation involved in crushing the cavity CV is added to the normal deformation by buckling as mentioned supra, so that the fender 9 encounters the correspondingly increased amount of deformation after buckling. This results in the greater decline of the reaction force after Maximum Point A. In contrast, the arrangement of claim 1 is adapted to reduce or totally eliminate the cavity between the bent members 11, 12 by virtue of a corner of the step 14 caught in the cavity, as shown in FIG. 2B. Thus, the decline of the reaction force after Maximum Point A is reduced.
According to the arrangement of claim 1, the synergy between these effects not only approximates the characteristic curve as close as possible to the idealistic curve but also enables further increase in the energy-absorption capacity and the energy absorption efficiency of the fender.
According to the invention of claim 2, the fender of claim 1 is characterized in that the first bumper member and the second bumper member share the same inside diameter at the connection portion and that a ratio T1/T2 is in the range of 0.8 to 0.9, T1 denoting a thickness of the first bumper member, T2 denoting a thickness of the second bumper member.
If the ratio T1/T2 is less than 0.8, the thickness T2 of the second bumper member 12 is relatively increased.
This may result in a similar problem to that occurred in the case of FIGS. 22A, 22B. Specifically, areas 12b, 12c above and below the buckling position BP on an inner periphery of the second bumper member 12 are brought into contact with each other by a smaller distortion and hence, the allowed distortion D is decreased. This leads to a reduced energy-absorption capacity after buckling.
If the ratio T1/T2 exceeds 0.9, the step 14 may have an insufficient dimension for adequately offering the effect of claim 1. Specifically, when caught in the cavity between the bent of the first and second bumper members 11, 12, the step 14 may not be effective enough to reduce or totally eliminate the cavity. Thus, the decline of the reaction force after Maximum Point A cannot be reduced enough. Or the step 14 may not be effective enough to increase the distortion involved in bringing the outer peripheries 11a, 12a of the bumper members 11, 12 into contact with each other. Thus, the distortion D cannot be increased enough.
In contrast, the arrangement of claim 2 is not likely to encounter these problems, further enhancing the effects of claim 1.
According to the invention of claim 3, the fender of claim 1 is characterized in that a ratio H1/H0 is in the range of 0.1 to 0.3, H1 denoting an axial height of the cylindrical body of the first bumper member, H0 denoting an overall height of the fender with respect to the axis of the cylindrical body.
According to the invention of claim 4, the fender of claim 3 is characterized in that an angle xcex81 between the fixing surface and a generatrix of the conical body of the second bumper member is in the range of 70 to 80xc2x0.
If the overall height H0 and the outside diameter D1 of the first bumper member 11 are constant, the height H1 and the angle xcex81 have a correlation. That is, as the height H1 of the first bumper member 11 accounts for the greater proportion of the overall height H0, the angle xcex81 becomes the smaller, as shown in FIG. 8. On the other hand, the angle xcex81 increases with decrease in the proportion of the height H1 as shown in FIG. 9.
If the height H1 is below the above range or if the angle xcex81 exceeds the above range, the reaction force at buckling is increased because the height H2 of the second bumper member 12 has a relatively increased proportion of the overall height H0. At the same time, the energy-absorption capacity as a whole is increased because the distortion of the fender involved in bringing the second bumper member 12 into a buckling process or the distortion thereof involved in buckling the second bumper member to limit is increased. Considering the characteristics of the fender, however, such a fender cannot serve a useful function because a width of a constant load area, that is, a range of the characteristic curve between Maximum Point A and the point B where the first bumper member 11 is in charge of the load is too small.
If the height H1 exceeds the above range or if the angle xcex81 is below the above range, the reaction force at buckling is decreased because the height H2 of the second bumper member 12 has a relatively decreased proportion of the overall height H0. At the same time, the distortion of the fender involved in bringing the second bumper member 12 into the buckling process or the distortion thereof involved in buckling the second bumper member to limit is decreased. Hence, the energy-absorption capacity as a whole tends to decrease.
In contrast, the arrangements of claims 3 and 4 are not likely to encounter these problems, further enhancing the effects of claim 1.
According to the invention of claim 5, a fender for absorbing the impact of a vessel, formed of rubber and fixed to a fixing surface of a dock as having an impact receiving plate secured to a distal end of its body, the fender comprises: a first bumper member formed in a cylindrical shape of a constant outside diameter and defining at one end of the cylindrical body thereof a fixing portion for the impact receiving plate; a second bumper member connected at one end to the other end of the cylindrical body of the first bumper member, defining at the other end thereof a fix portion to be fixed to the fixing surface, formed in a hollow conical shape with its latter end greater in outside diameter than its former end, and buckling radially outwardly upon receiving a compressive force from the vessel thereby absorbing the impact of the vessel; and a projection having a constant width and formed along a buckling position on an inner periphery of the second bumper member.
According to the arrangement of claim 5, the second bumper member 12 is buckled and clamp a projection 15 from top and bottom, as shown in FIG. 4C while the clamped projection 15 develops a counterforce against a compressive force applied thereto by being buckled. That is, the projection 15 contributes the counterforce against the buckling of the second bumper member 12. This results in an increased reaction force which the buckled second bumper member 12 exhibits against the compressive force.
On the inner periphery of the second bumper member 12, the areas 12b, 12c above and below the projection 15 are in somewhat recessed from the projection 15. This also results in an increased distortion of the buckled fender which is involved in bringing the areas 12b, 12c into contact with each other.
Thus, the synergy between these effects increases the energy-absorption capacity of the fender as a whole.
According to the invention of claim 6, the fender of claim 5 is characterized in that a ratio W1/W2 is in the range of 3/6 to 6/3, W1 denoting a distance from the buckling position to an upper side of the projection along an axis of the conical body of the second bumper member, W2 denoting a distance from the buckling position to a lower side of the projection along the axis of the conical body.
If the ratio W1/W2 is less than 3/6, the upper side of the projection 15 is so close to the buckling position BP of the second bumper member 12 that the second bumper member 12 buckles only along the upper side of the projection 15 as shown in FIG. 12C for example. If the ratio W1/W2 is in excess of 6/3, the lower side of the projection 15 is so close to the buckling position BP of the second bumper member 12 that the second bumper member 12 buckles only along the lower side of the projection 15 as shown in FIG. 13C for example. In either cases, the buckled second bumper member 12 cannot clamp the projection 15 from top and bottom well, thus, the effect of claim 5 may not be fully attained.
In contrast, the arrangement of claim 6 is not likely to encounter these problems, further enhancing the effects of claim 5.
According to the invention of claim 7, the fender of claim 6 is characterized in that a distance W1+W2 between the upper side and the lower side of the projection along the axis of the conical body is in the range of 20 to 40% of a height H2 of the second bumper member along the axis of the conical body.
If the distance W1+W2 representative of the width of the projection 15 is less than 20% of the height H2, the projection 15 may not provide the adequate effects of claim 5. Specifically, the projection 15 may be too small to afford the aforesaid effect to increase the reaction force of the second bumper member 12 as it is buckled. If the distance W1+W2 is in excess of 40% of the height H2, a similar result to that of the increased thickness of the whole body of the second bumper member 12 is produced. This leads to the same problem as in the case of FIGS. 22A, 22B, decreasing the energy-absorption capacity after buckling.
In contrast, the arrangement of claim 7 is not likely to encounter these problems, further enhancing the effects of claim 5.
According to the invention of claim 8, the fender of claim 7 is characterized in that the projection is of a trapezoidal shape in section and has a projection height T3 from the inner periphery of the second bumper member in the range of 5 to 15% of the thickness T2 of the second bumper member.
If the height T3 of the projection 15 of the trapezoidal sectional shape is less than 5% of the thickness T2 of the second bumper member, the projection 15 may be too low to afford an adequate effect to increase the reaction force of the second bumper member 12 as it is buckled. It is also likely that the projection 15 is not effective enough to increase the distortion of the buckled fender involved in bringing the areas 12b, 12c above and below the projection 15 into contact with each other. That is, the provision of the projection 15 may not contribute the adequate effect. If the height T3 of the projection 15 exceeds 15% of the thickness T2 of the second bumper member, an excessive distortion of the fender may be involved in bringing the areas 12b, 12c into contact with each other, the areas 12b, 12c located above and below the projection 15 on the inner periphery of the second bumper member 12. As a result, the fender is excessively distorted when both the areas 12b, 12c contact each other so that the reaction force rises sharply after this point of time, i.e., after the point C on the reaction force characteristic curve. That is, the fender is excessively compressed so that damage to the vessel or the fender itself may result.
In contrast, the arrangement of claim 8 is not likely to encounter these problems, further enhancing the effects of claim 5.
According to the invention of claim 9, the fender of claim 7 is characterized in that the projection is of a triangular shape in section and has a projection height T3 from the inner periphery of the second bumper member in the range of 15 to 20% of the thickness T2 of the second bumper member. Given the same width and height, the projection 15 of the triangular sectional shape has a smaller sectional area than the projection of the trapezoidal sectional shape. Accordingly, the projection is designed to have a greater projection height T3 in order to accomplish the same degree of working effect as the projection of the trapezoidal sectional shape.
If the projection of the triangular sectional shape has a projection height T3 of less than 15% of the thickness T2 of the second bumper member 12, the projection 15 may be too low to afford an adequate effect to increase the reaction force of the second bumper member 12 as it is buckled. It is also likely that the projection 15 is not effective enough to increase the distortion of the buckled fender involved in bringing the areas 12b, 12c above and below the projection 15 into contact with each other. That is, the provision of the projection may not contribute the adequate effect. If the height T3 of the projection 15 exceeds 20% of the thickness T2 of the second bumper member, an excessive distortion of the fender may be involved in bringing the areas 12b, 12c into contact with each other, the areas 12b, 12c located above and below the projection 15 on the inner periphery of the second bumper member 12. The fender is excessively distorted when both the areas 12b, 12c contact each other so that the reaction force rises sharply after this point of time, i.e., after the point C on the reaction force characteristic curve. That is, the fender is excessively compressed so that damage to the vessel or the fender itself may result.
In contrast, the arrangement of claim 9 is not likely to encounter these problems, further enhancing the effects of claim 5.
According to the invention of claim 10, the fender of claim 5 further comprises a step along an outer periphery of a connection portion between the two bumper members, the step defined by the former end of the second bumper member having a greater outside diameter than the latter end of the first bumper member.
According to the arrangement of claim 10, the synergy between the effects of the arrangements of claims 1 and 5 not only provides the characteristic curve even closer to the idealistic curve but also enables further increase in the energy-absorption capacity and the energy absorption efficiency of the fender.
An analogous arrangement to the inventive arrangement is disclosed in Japanese Unexamined Patent Publication No.11(1999)-222833 which suggests the provision of a step on an outer periphery of a circle-type fender. However, this step is not provided at the connection portion between the first and the second bumper members but at a midportion of the second bumper member, which is far below the connection portion. Disposed at such a place, the step does not operate the same way as the aforementioned step of the invention. Therefore, the above fender cannot offer the working effect equivalent to that of the invention. Hence, this prior art is not construed as disclosing nor suggesting the present invention.
Japanese Unexamined Patent Publication No.7(1995)-229129 discloses a circle-type fender provided with a projection on its inner periphery. However, the projection is not disposed on the buckling position of the fender, as shown in FIG. 8, contained in this official gazette. The projection is disposed in a manner that the buckling position is positioned on a boundary between the projection and a smaller-thickness portion adjoining thereto. Therefore, this fender is no more than an equivalent to the aforementioned comparative examples of FIGS. 12A-12C and 13A-13C, being unable to offer the same working effect as the invention. Hence, this prior art is not construed as disclosing nor suggesting the present invention.
Further, Japanese Examined Utility Publication No.49(1974)-15516 discloses a fender, the whole body of which is formed in a cylindrical shape of a constant outside diameter. This prior-art fender has an arrangement wherein the cylindrical body is formed with a projection at its buckling position. However, this prior art never teaches that the whole body of the fender consists of a first cylindrical bumper member of a constant outside diameter and a second bumper member of a hollow conical shape, nor that the projection is disposed on the buckling position of the second bumper member. Hence, this prior art is not construed as disclosing nor suggesting the present invention.